Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$81.98	9.494%	$89.7632	$89.76	$89.75	$89.80
Purchase #2	$89.97	3.172%	$92.8238	$92.82	$92.80	$92.80
Purchase #3	$208.82	11.771%	$233.4002	$233.40	$233.40	$233.40
Purchase #4	$60.51	11.796%	$67.6478	$67.65	$67.65	$67.60
Purchase #5	$54.74	12.171%	$61.4024	$61.40	$61.40	$61.40
Purchase #6	$44.46	5.656%	$46.9747	$46.97	$46.95	$47.00
Purchase #7	$153.79	3.138%	$158.6159	$158.62	$158.60	$158.60
7 purchase totals =	$694.27		$750.6280	$750.62	$750.55	$750.60